Effects of Applied and Residual Stress on the Magnetoresistance of Nickel

Abstract

The magnetoresistance of annealed nickel was measured under both tensile and compressive stresses up to 10 000 lb/in.² (7.0 kg/mm²). The zero‐stress value of ΔR/R (1.88%) was increased to 2.48% by tension and decreased to 0.29% by compression. The magnetoresistance was also measured after increasing amounts of plastic elongation; the values of ΔR/R measured at 550 Oe were found to decrease with increasing amounts of plastic strain. This result is compatible with a residual microstress distribution in which the volume fraction of the specimen in compression equals or exceeds the volume fraction in tension. The elastoresistance ΔR/R of annealed nickel was found to be 1.46% at 8000 lb/in.² compression (5.6 kg/mm²) and −0.60% for the same stress in tension. Elastoresistance measurements on deformed specimens do not lead to any conclusions about the residual stress state.